Photolithography is widely used in semiconductor manufacture and other applications. During photolithography, an exposure energy, such as ultraviolet light, is passed through a mask and onto a target such as a semiconductor wafer. The mask contains opaque and transparent regions which form a primary mask pattern. The exposure energy exposes the mask pattern on a layer of resist deposited on the target. Following exposure, the layer of resist can be developed to form a resist mask. In semiconductor manufacture, such a resist mask can be used for etching, ion implantation, screen printing, CVD and other processes.
One recently developed form of lithography uses a laser scanner to focus modulated laser beams in a series of scan lines onto a radiant sensitive film of resist. This technique eliminates the mask, as the pattern is written directly onto the resist. A conventional laser scanner includes a laser adapted to generate a collimated light beam, that can be split into an array of collimated sub beams. Typically, the laser beam comprises ultraviolet light having a wavelength of 325 nm or 363.8 nm. The laser scanner also includes a modulator, such as an acousto-optic modulator, adapted to receive a data signal in digital form, and to modulate the laser beam responsive to the data signal. In addition, the laser scanner includes scan optics, such as a rotating reflective polygon, adapted to form an image of the beam and to sweep the image across a scan line. The laser scanner also includes a precision stage adapted to move the target in X and Y directions approximately perpendicular to the scan line direction.
The present invention employs a laser scanner and direct laser imaging to improve various wafer level fabrication and test processes for semiconductor components. For example, semiconductor dice, semiconductor packages, and semiconductor interconnects are typically fabricated on a single substrate (e.g., wafer or panel) that is subsequently singulated into individual components. These processes are sometimes referred to as being “wafer level” processes.
One shortcoming of wafer level fabrication processes is that some of the components on the substrate can be defective. For example, defects can occur in the integrated circuits contained on the components, in the address circuitry for the components, or in the configuration of the arrays of semiconductor devices on the components. Some defects can make a component non-functional, while other defects merely affect the electrical characteristics of the component.
The defective components can decrease the yield of the substrate and affect the quality of the singulated components. In addition, the defective components can compromise subsequent test procedures, particularly wafer level burn-in tests. For example, conventional burn-in boards utilize “shared resources” wherein multiple components are electrically connected in series, and the same test signals are applied to multiple components. Defective components can short the test signals, and adversely affect the test process.
Rather than having specific defects, other semiconductor components can have electrical characteristics that do not meet certain standards. For example, one important electrical characteristic is the speed with which the components process signals. Some functional components can have speed characteristics that make the components unsuitable for a particular application. Again the substandard components can decrease the yield of the substrate.
The present invention utilizes a laser scanner and direct laser imaging to improve wafer level fabrication and test processes for semiconductor components.